Essential role of Mg2+ in mouse preimplantation embryo development revealed by TRPM7 chanzyme-deficient gametes

TRPM7 underlies cadmium cytotoxicity in pulmonary cells

TRPM7 is a kinase-coupled ion channel that exhibits high activity in the immune and epithelial cells of different organs, including the lung. Electrophysiological studies have established that the TRPM7 channel displays high permeability to Mg2+, Zn2+, and Ca2+, as well as trace metal cations. While the critical role of TRPM7 in the cellular balance of Mg2+, Zn2+, and Ca2+ is well-documented, its contribution to the cellular uptake of trace metal cations, frequent respiratory pollutants, remains unclear. Here, we performed an electrophysiological assessment of pulmonary A549 cells revealing endogenous TRPM7 currents, which were eliminated by knockout (KO) of the TRPM7 gene using the CRISPR/Cas9 approach or by administration of NS8593 and VER155008, two structurally unrelated inhibitors of the TRPM7 channel. Unlike prior studies with various cell lines showing that TRPM7 KO mutation induces cell growth arrest, we observed that A549 cells maintained normal viability after genetic and pharmacological inactivation of TRPM7. Consequently, we used A549 cells to examine the impact of Cd2+ on cell viability and found that TRPM7 KO mutation and both pharmacological agents mitigated the Cd2+ cytotoxicity. Analogous to A549 cells, electrophysiological analysis of mouse primary alveolar type 2 (ATII) cells revealed endogenous TRPM7 currents and Cd2+ exposure reduced the cell viability of ATII cells in a TRPM7-dependent fashion. Hence, the TRPM7 channel contributes to Cd2+ cytotoxicity in pulmonary cells and can serve as a therapeutic target to alleviate the toxic effects of trace metal exposure.

The TRPV3 channel is a mediator of zinc influx and homeostasis in murine oocytes

Zinc (Zn2+) homeostasis is essential for gametogenesis and reproduction, and its deficiency causes infertility. Oocytes contain higher Zn2+ levels than somatic cells, and Zn2+ concentrations in oocytes are far higher than those of other transition metals and increase even more during maturation in preparation for fertilization. Remarkably, it is unknown what transporter(s) or channel(s) mediate Zn2+ influx in oocytes and whether they are expressed uniformly throughout folliculogenesis. Here, we showed that the functional expression of a member of the transient receptor potential family, vanilloid 3, TRPV3, closely follows the dynamics of intracellular Zn2+ during oocyte maturation, raising the prospect that these events may be functionally linked. Using microfluorometry, we monitored in oocytes of Trpv3 null females the expected rise in Zn2+ concentrations during maturation. Surprisingly, Zn2+ levels did not climb, and the overall FluoZin3 signal in Trpv3 null eggs was lower than in control eggs. Electrophysiological recordings showed a large TRPV3 current induced by the agonist 2-APB in WT eggs supplemented with extracellular Zn2+ that was absent in Trpv3 null eggs; TRPV3 showed a clear preference for Zn2+ over Ca2+. Trpv3 null eggs displayed features associated with Zn2+ deficient conditions, such as lower IP3R1 function, abnormal cortical granule distribution, and disturbed cytoskeletal organization with distinct actin nucleation disorders. Notably, Trpv3 null eggs demonstrated undisturbed Zn2+ sparks. Our results suggest that TRPV3 is a pivotal member of the Zn2+ toolkit, mediating Zn2+ intake during maturation. They also indicate that distinct transporters or channels mediate Zn2+ influx throughout folliculogenesis.

Mg2+ Supplementation Mitigates Metabolic Deficits Associated With TRPM7 Disruption

Transient receptor potential channel subfamily M member 7 (TRPM7) regulates cellular and systemic Mg2+ homeostasis through its channel domain and induces protein phosphorylation via its kinase domain. We recently found that mice with selective deletion of Trpm7 in β-cells develop glucose intolerance and declines in insulin secretion, primarily due to the impaired enzymatic activity of this protein. Accumulating evidence suggests that Mg2+ supplementation effectively mitigates the detrimental effects of TRPM7 disruption in various cell types. However, the impact of Mg2+ supplementation on metabolic impairments caused by TRPM7 inactivation remains unclear. In the present study, we found that Mg2+ supplementation significantly ameliorates glucose intolerance observed in high-fat-fed TRPM7 kinase-deficient mice (Trpm7R/R). However, our ex vivo analysis of islets isolated from Trpm7R/R mice revealed that Mg2+ supplementation does not enhance glucose-induced insulin secretion. Instead, the improvement appears to be partially driven by enhanced insulin sensitivity and increased β-cell proliferation. The pharmacological analysis in MIN6 cells showed that inhibiting TRPM7 with either NS8593 or VER155008 disrupts β-cell proliferation. These effects mimicked the phenotype seen in Trpm7R/R mice. We attribute this impairment to diminished ERK1/2 signaling, which suppressed PDX1 expression, while Mg2+ supplementation in vitro partially restored ERK1/2 phosphorylation levels. Collectively, Mg2+ supplementation enhances glucose metabolism in Trpm7R/R mice and mitigates the ERK1/2 signaling disruptions and proliferation arrest induced by TRPM7 inactivation in vitro. These findings provide compelling evidence that Mg2+ supplementation can reverse the adverse metabolic and cellular phenotypes associated with the loss of TRPM7 function.

Calcium signaling in oocyte quality and functionality and its application

Calcium (Ca2+) is a second messenger for many signal pathways, and changes in intracellular Ca2+ concentration ([Ca2+]i) are an important signaling mechanism in the oocyte maturation, activation, fertilization, function regulation of granulosa and cumulus cells and offspring development. Ca2+ oscillations occur during oocyte maturation and fertilization, which are maintained by Ca2+ stores and extracellular Ca2+ ([Ca2+]e). Abnormalities in Ca2+ signaling can affect the release of the first polar body, the first meiotic division, and chromosome and spindle morphology. Well-studied aspects of Ca2+ signaling in the oocyte are oocyte activation and fertilization. Oocyte activation, driven by sperm-specific phospholipase PLCζ, is initiated by concerted intracellular patterns of Ca2+ release, termed Ca2+ oscillations. Ca2+ oscillations persist for a long time during fertilization and are coordinately engaged by a variety of Ca2+ channels, pumps, regulatory proteins and their partners. Calcium signaling also regulates granulosa and cumulus cells' function, which further affects oocyte maturation and fertilization outcome. Clinically, there are several physical and chemical options for treating fertilization failure through oocyte activation. Additionally, various exogenous compounds or drugs can cause ovarian dysfunction and female infertility by inducing abnormal Ca2+ signaling or Ca2+ dyshomeostasis in oocytes and granulosa cells. Therefore, the reproductive health risks caused by adverse stresses should arouse our attention. This review will systematically summarize the latest research progress on the aforementioned aspects and propose further research directions on calcium signaling in female reproduction.

TRPM7 in neurodevelopment and therapeutic prospects for neurodegenerative disease

Neurodevelopment, a complex and highly regulated process, plays a foundational role in shaping the structure and function of the nervous system. The transient receptor potential melastatin 7 (TRPM7), a divalent cation channel with an α-kinase domain, mediates a wide range of cellular functions, including proliferation, migration, cell adhesion, and survival, all of which are essential processes in neurodevelopment. The global knockout of either TRPM7 or TRPM7-kinase is embryonically lethal, highlighting the crucial role of TRPM7 in development in vivo. Subsequent research further revealed that TRPM7 is indeed involved in various key processes throughout neurodevelopment, from maintaining pluripotency during embryogenesis to regulating gastrulation, neural tube closure, axonal outgrowth, synaptic density, and learning and memory. Moreover, a discrepancy in TRPM7 expression and/or function has been associated with neuropathological conditions, including ischemic stroke, Alzheimer's disease, and Parkinson's disease. Understanding the mechanisms of proper neurodevelopment may provide us with the knowledge required to develop therapeutic interventions that can overcome the challenges of regeneration in CNS injuries and neurodegenerative diseases. Considering that ion channels are the third-largest class targeted for drug development, TRPM7's dual roles in development and degeneration emphasize its therapeutic potential. This review provides a comprehensive overview of the current literature on TRPM7 in various aspects of neurodevelopment. It also discusses the links between neurodevelopment and neurodegeneration, and highlights TRPM7 as a potential therapeutic target for neurodegenerative disorders, with a focus on repair and regeneration.